1. Field of the Invention
The present invention relates to the detection of the positions of selected valves in an internal combustion engine to determine whether the crank shaft is oriented at a position identified as the 0.degree. position or the 360.degree. position. In particular the invention relates to detection of the position of valve retainers to discover misassembly of components associated with the valves while identifying the angular location of the 0.degree. and 360.degree. positions.
2. Description of the Prior Art
The adjustment of valve clearance in internal combustion engines on a production line has heretofore been carried out manually by making visual observation of the valve stems and assemblies. In order to mechanize valve clearance adjustment, it is necessary to detect certain angular positions of the crank shaft identified by ultimate phases of the top dead center of a selected piston in the compression stroke and in the exhaust stroke. It is well known that, in a 4-cycle internal combustion engine, the position of the crank shaft is exactly the same when a given piston is at its top dead center in the compression stroke and in the exhaust stroke, but the positions of the valves of that cylinder are not the same for the two top dead center positions. Adjustment of valve clearance by automatic means also requires that the valves and cotters be checked for proper assembly.
The conventional practice for observing the valve locations to determine top dead center positions of the piston in the first cylinder of the engine include watching the intake and exhaust valves of the first cylinder to see that the rocker arms controlling these valves are in contact with the base circle portions of the respective cam lobes. If they are, and if a clearance can be seen between the ends of the valve stems and the rocker arms, the piston of the first cylinder is considered to be in its top dead center position in the compression stroke, but if there is no clearance between the rockers and the valve stems, the piston of the cylinder is considered to be in its top dead center position in the exhaust stroke.
The proper assembly of the valve components has been determined by visual inspection of the cotters of the intake and exhaust valves of the engine, and no automatic mechanical means of doing this task have been available heretofore.